1. Field of the Invention
The present invention relates to a high-accuracy timepiece the accuracy adjustment of which can be made in an assembled state and in which accuracy readjustment is not necessary even after a power supply has been temporarily removed. More particularly, the invention is directed to an inexpensive high-accuracy timepiece in which accuracy adjustment can be made by operating a crown or other external input means.
2. Description of the Prior Art
A high-accuracy timepiece guaranteeing an accuracy of 10 seconds a year is now marketed together with an ordinary accuracy timepiece guaranteeing an accuracy of 15 seconds a month. For assembling the high-accuracy timepiece from a movement state to a complete state, one cannot ignore accuracy errors caused by the pressure applied to the crystal oscillator, the floating capacitances fluctuating from one component to another and the like. Therefore, it is necessary to make accuracy adjustments in the complete state. An accuracy adjustment of a conventional high-accuracy timepiece is made in the complete state as follows. A reference signal lasting for a predetermined time period is inputted off line, and the inputted reference signal is compared with a internal signal to thereby measure a deviation from a reference rate, and rate adjustment data, known as rate fast/slow data or logical acceleration/deceleration data (logic fast/slow data for correcting the deviation from the reference rate) is stored in a writable nonvolatile memory such as an EEPROM. In a digital timepiece disclosed in Japanese Patent Application Laid-Open No. Sho 56-168187, an accuracy adjustment is made by setting rate fast/slow data while operating a button, and storing the data in a volatile memory.
The former conventional technology has addressed the problem that it requires a receiving circuit to be added inside the timepiece and new manufacturing equipment for outputting a reference signal to be provided. Further, a writable nonvolatile memory such as an EEPROM is comparatively expensive among other components of the timepiece, and thus the use of the memory has elevated the cost of the timepiece. On the other hand, the latter conventional technology has addressed the following problems. Since the set rate fast/slow data is erased when a power supply is replaced, the rate must be readjusted. In addition, a button and a liquid crystal display must be provided for inputting the rate fast/slow data, and thus an analog timepiece without a button and a liquid crystal display cannot be applied to a high-accuracy timepiece.
The present invention has been made in view of the aforementioned circumstances, and therefore an object thereof is to provide an inexpensive high-accuracy timepiece which allows rate fast/slow data to be inputted in a complete state and which does not allow the rate fast/slow data to be deleted even when a power supply is replaced.
A high-accuracy timepiece according to the present invention allows rate fast/slow data to be inputted from a crown that is already provided on the timepiece in order to allow the rate fast/slow data to be inputted in a complete state even if a receiving circuit and a button are not provided. Further, the high-accuracy timepiece includes data storage means such as an EEPROM which is writable and which allows data stored before a power supply is temporarily removed to remain unchanged even after the power supply has been temporarily removed so that the rate fast/slow data and other data is not deleted when the power supply has been replaced.
Here, in inputting the rate fast/slow data, the day wheel is used not only to determine what operation has been performed by an external part at what timing but also to give an indication for inputting the rate fast/slow data and for checking the stored rate fast/slow data. Further, the second hand, the minute hand or the hour hand may be used to do the same in place of the day wheel. Still further, the day wheel may be driven by another motor, or the same motor using an oscillation mechanism.
Further, by allowing two sets of rate fast/slow data for making a rough adjustment and a fine adjustment to be stored in separate means, the timepiece is arranged so as not to lose its accuracy to so large an extent even in the case where the rate fast/slow data for making a fine adjustment has been deleted.
Next, a volatile memory and a power backup capacitor are used jointly as data storage means in place of an expensive writable nonvolatile memory, thereby reducing the cost. Still further, by using power supply removal detection means for detecting removal of a power supply and oscillation control means for controlling oscillation means to stop or resume an oscillation, the power consumption is suppressed.
Further, by using data holding determination means, whether or not data in the data storage means has been held is determined, and the determination result is indicated on indication means.
Here, when the oscillation control means has determined that the power supply has been removed, first, the data storage means stores a plurality of copied data such as the rate fast/slow data. Then, when the operation of resuming an oscillation has been performed by inserting a new power supply, the data holding determination means obtains the plurality of copied data that have been stored and determines whether the data has been held by comparing the obtained data. The determination result is indicated on the indication means.